This invention relates to the art of diagnosing various blood related parameters of a patient with apparatus connected to but located externally of a patient's body.
The invention is particularly applicable in conjunction with analyzing blood related parameters with respect to the vascular system and is described with particular reference thereto, although it is to be appreciated that the invention may be applied in other body systems.
It is known in the art to provide externally located devices for use in monitoring various parameters of blood flowing in the cardiovascular system of a patient. Such devices may, for example, take the form of a single lumen in-dwelling catheter installed in a patient's blood vessel so as to have access to the cardiovascular system. A separate catheter is employed, each having access to a patient's blood vessel, for each blood parameter to be monitored. It is frequently necessary to move the location of each catheter at periodic intervals, such as every 72 hours, and each new location requires a new puncture into the patient's blood vessel. This causes patient discomfort as well as the chances for complications.
It is, therefore, desirable when monitoring several parameters of blood in the cardiovascular system, that a single access to a patient's blood vessel be obtained to accommodate monitoring of all parameters.
The prior art recognizes the desirability of having a single access to a patient's blood vessel, as is evident by U.S. Pat. No. 4,072,146 to Howes. Howes proposes a system wherein a single catheter is inserted into a patient's blood vessel. But the catheter has a plurality of lumens each providing a passageway for conveying fluid; one for obtaining blood samples, another for use communicating with a source of IV fluid and another for use in intraveneous pressure monitoring. While such a system provides a single access, it nevertheless requires a catheter of sufficient diameter to accommodate the three lumens while still being of a size to enter into a patient's blood vessel. This diameter limits the number of parameters that may be monitored to that of the number of lumens within the catheter.
It is desirable to provide a blood monitoring system employing a catheter having but a single lumen and having a single access into a patient's blood vessel while permitting several parameters of blood to be monitored.
Typically, prior art systems involving external devices for measuring blood pressure or obtaining blood samples and the like include a confusing array of lines, valves, various adjustments, and a multitude of couplings which presents the potential for leakage. Such is illustrated, for example, in the aforementioned U.S. Pat. No. 4,072,146 to Howes. Another example, for blood pressure monitoring, is illustrated by the U.S. Pat. No. 4,431,009 to Marino et al.
It is desirable in such a system to employ a single valve actuator for controlling both blood flow and parenteral flow to avoid confusion during operation.